I am cutting chambers into all of the wood except the outside curly redwood. The balsa I bought had to be at least 3 1/2 x 5 x 9-6. I ended up getting some very heavy wood. These are wall hangers, so that doesn’t matter on the wall. However, super heavy boards are a hassle to shape.
I weighed one of the heavier pieces at 19.6 lbs. After chambering, it weighed 12.6 lbs.
The final cut is done with a sabre saw. I located a blade that is just long enough. This method is faster than trying to use only the sabre saw. Also, it tends to wander on the other side. I know, as I messed up one piece already.